As in “Before testing or reconfiguring, always mount a
scratch monkey”, a proverb used to advise
caution when dealing with irreplaceable data or devices. Used to refer to
any scratch volume hooked to a computer during any risky operation as a
replacement for some precious resource or data that might otherwise get
trashed.

This term preserves the memory of Mabel, the Swimming Wonder Monkey,
star of a biological research program at the University of Toronto. Mabel
was not (so the legend goes) your ordinary monkey; the university had spent
years teaching her how to swim, breathing through a regulator, in order to
study the effects of different gas mixtures on her physiology. Mabel
suffered an untimely demise one day when a DECfield circus engineer troubleshooting a crash on the
program's VAX inadvertently interfered with some
custom hardware that was wired to Mabel.

It is reported that, after calming down an understandably irate
customer sufficiently to ascertain the facts of the matter, a DEC
troubleshooter called up the field circus manager
responsible and asked him sweetly, “Can you swim?” Not all the
consequences to humans were so amusing; the sysop of the machine in
question was nearly thrown in jail at the behest of certain clueless
droids at the local ‘humane’ society.
The moral is clear: When in doubt, always mount a scratch monkey. [The
actual incident occured in 1979 or 1980. There is a version of this story,
complete with reported dialogue between one of the project people and DEC
field service, that has been circulating on Internet since 1986. It is
hilarious and mythic, but gets some facts wrong. For example, it reports
the machine as a PDP-11 and alleges that Mabel's demise occurred when DEC
PMed the machine. Earlier versions of this entry
were based on that story; this one has been corrected from an interview
with the hapless sysop. —ESR]